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Chen D, Motlagh SAO, Stappen FV, Labarbe R, Bell B, Kim M, Teo BKK, Dong L, Zou W, Diffenderfer ES. Secondary neutron dosimetry for conformal FLASH proton therapy. Med Phys 2024. [PMID: 38597815 DOI: 10.1002/mp.17050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 03/12/2024] [Accepted: 03/13/2024] [Indexed: 04/11/2024] Open
Abstract
BACKGROUND Cyclotron-based proton therapy systems utilize the highest proton energies to achieve an ultra-high dose rate (UHDR) for FLASH radiotherapy. The deep-penetrating range associated with this high energy can be modulated by inserting a uniform plate of proton-stopping material, known as a range shifter, in the beam path at the nozzle to bring the Bragg peak within the target while ensuring high proton transport efficiency for UHDR. Aluminum has been recently proposed as a range shifter material mainly due to its high compactness and its mechanical properties. A possible drawback lies in the fact that aluminum has a larger cross-section of producing secondary neutrons compared to conventional plastic range shifters. Accordingly, an increase in secondary neutron contamination was expected during the delivery of range-modulated FLASH proton therapy, potentially heightening neutron-induced carcinogenic risks to the patient. PURPOSE We conducted neutron dosimetry using simulations and measurements to evaluate excess dose due to neutron exposure during UHDR proton irradiation with aluminum range shifters compared to plastic range shifters. METHODS Monte Carlo simulations in TOPAS were performed to investigate the secondary neutron production characteristics with aluminum range shifter during 225 MeV single-spot proton irradiation. The computational results were validated against measurements with a pair of ionization chambers in an out-of-field region ( ≤ $\le$ 30 cm) and with a Proton Recoil Scintillator-Los Alamos rem meter in a far-out-of-field region (0.5-2.5 m). The assessments were repeated with solid water slabs as a surrogate for the conventional range shifter material to evaluate the impact of aluminum on neutron yield. The results were compared with the International Electrotechnical Commission (IEC) standards to evaluate the clinical acceptance of the secondary neutron yield. RESULTS For a range modulation up to 26 cm in water, the maximum simulated and measured values of out-of-field secondary neutron dose equivalent per therapeutic dose with aluminum range shifter were found to be( 0.57 ± 0.02 ) mSv/Gy $(0.57\pm 0.02)\ \text{mSv/Gy}$ and( 0.46 ± 0.04 ) mSv/Gy $(0.46\pm 0.04)\ \text{mSv/Gy}$ , respectively, overall higher than the solid water cases (simulation:( 0.332 ± 0.003 ) mSv/Gy $(0.332\pm 0.003)\ \text{mSv/Gy}$ ; measurement:( 0.33 ± 0.03 ) mSv/Gy $(0.33\pm 0.03)\ \text{mSv/Gy}$ ). The maximum far out-of-field secondary neutron dose equivalent was found to be (8.8 ± 0.5 $8.8 \pm 0.5$ ) μ Sv / Gy $\umu {\rm Sv/Gy}$ and (1.62 ± 0.02 $1.62 \pm 0.02$ ) μ Sv / Gy $\umu {\rm Sv/Gy}$ for the simulations and rem meter measurements, respectively, also higher than the solid water counterparts (simulation: (3.3 ± 0.3 $3.3 \pm 0.3$ ) μ Sv / Gy $\umu {\rm Sv/Gy}$ ; measurement: (0.63 ± 0.03 $0.63 \pm 0.03$ ) μ Sv / Gy $\umu {\rm Sv/Gy}$ ). CONCLUSIONS We conducted simulations and measurements of secondary neutron production under proton irradiation at FLASH energy with range shifters. We found that the secondary neutron yield increased when using aluminum range shifters compared to conventional materials while remaining well below the non-primary radiation limit constrained by the IEC regulations.
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Affiliation(s)
- Dixin Chen
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | | | | | - Rudi Labarbe
- Ion Beam Applications S.A. (IBA), Louvain-la-Neuve, Belgium
| | - Beryl Bell
- Ion Beam Applications S.A. (IBA), Louvain-la-Neuve, Belgium
| | - Michele Kim
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Boon-Keng Kevin Teo
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Lei Dong
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Wei Zou
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Tawonwong T, Suriyapee S, Dachviriyakij T, Pungkun V, Ruangchan S, Sanghangthum T. Measurement of Ambient Dose Equivalent in Compact Proton Therapy using In-house Neutron Moderator-based Poly Allyl Diglycol Carbonate. J Med Phys 2023; 48:243-247. [PMID: 37969145 PMCID: PMC10642591 DOI: 10.4103/jmp.jmp_35_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 06/14/2023] [Accepted: 06/15/2023] [Indexed: 11/17/2023] Open
Abstract
Purpose The high-energy proton produces the unwanted dose contribution from the secondary neutron. The main purpose of this study is to report the validation results of in-house neutron moderator based on poly allyl diglycol carbonate (CR-39) detector, Chulalongkorn University Neutron Moderator (CUMOD) through the ambient dose equivalent, H*(10) measurement. Materials and Methods The Particle and Heavy Ion Transport code System (PHITS) Monte Carlo code was used to simulate the neutron response function. The CUMOD was calibrated with 241AmBe source calibrator in the range of 100-1000 μSv. The variation of neutron fields was generated employing different proton treatment plans covering most of the clinical scenarios. The ambient dose equivalents, H*(10), evaluated employing CUMOD were compared to those obtained with WENDI-II dosimeter. Results The linear relationship between CUMOD and WENDI-II responses showed an R2 value close to 1. The H*(10) per Gy delivered dose was in the range of 22-105 μSv for a 10 cm × 10 cm field. Conclusion The in-house CUMOD neutron moderator can expand the neutron detection dose range of CR-39 detector for ambient dose equivalent. The advantage of CUMODs is its capability to evaluate H*(10) in various positions simultaneously.
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Affiliation(s)
- Tanawat Tawonwong
- Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
- Her Royal Highness Princess Maha Chakri Sirindhorn Proton Center, Bangkok, Thailand
- Department of Radiology, Division of Radiation Oncology, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
| | - Sivalee Suriyapee
- Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
- Department of Radiology, Division of Radiation Oncology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
| | - Tanapol Dachviriyakij
- Nuclear and Radiation Metrology Section, Regulatory Support Division, Office of Atoms for Peace, Bangkok, Thailand
| | - Vithit Pungkun
- Nuclear and Radiation Metrology Section, Regulatory Support Division, Office of Atoms for Peace, Bangkok, Thailand
| | - Sirinya Ruangchan
- Her Royal Highness Princess Maha Chakri Sirindhorn Proton Center, Bangkok, Thailand
- Department of Radiology, Division of Radiation Oncology, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
| | - Taweap Sanghangthum
- Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
- Her Royal Highness Princess Maha Chakri Sirindhorn Proton Center, Bangkok, Thailand
- Department of Radiology, Division of Radiation Oncology, King Chulalongkorn Memorial Hospital, Thai Red Cross Society, Bangkok, Thailand
- Department of Radiology, Division of Radiation Oncology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
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Leite AMM, Ronga MG, Giorgi M, Ristic Y, Perrot Y, Trompier F, Prezado Y, Créhange G, De Marzi L. Secondary neutron dose contribution from pencil beam scanning, scattered and spatially fractionated proton therapy. Phys Med Biol 2021; 66. [PMID: 34673555 DOI: 10.1088/1361-6560/ac3209] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 10/21/2021] [Indexed: 11/11/2022]
Abstract
The Orsay Proton therapy Center (ICPO) has a long history of intracranial radiotherapy using both double scattering (DS) and pencil beam scanning (PBS) techniques, and is actively investigating a promising modality of spatially fractionated radiotherapy using proton minibeams (pMBRT). This work provides a comprehensive comparison of the organ-specific secondary neutron dose due to each of these treatment modalities, assessed using Monte Carlo (MC) algorithms and measurements. A MC model of a universal nozzle was benchmarked by comparing the neutron ambient dose equivalent,H*(10), in the gantry room with measurements obtained using a WENDI-II counter. The secondary neutron dose was evaluated for clinically relevant intracranial treatments of patients of different ages, in which secondary neutron doses were scored in anthropomorphic phantoms merged with the patients' images. The MC calculatedH*(10) values showed a reasonable agreement with the measurements and followed the expected tendency, in which PBS yields the lowest dose, followed by pMBRT and DS. Our results for intracranial treatments show that pMBRT yielded a higher secondary neutron dose for organs closer to the target volume, while organs situated furthest from the target volume received a greater quantity of neutrons from the passive scattering beam line. To the best of our knowledge, this is the first study to compare MC secondary neutron dose estimates in clinical treatments between these various proton therapy modalities and to realistically quantify the secondary neutron dose contribution of clinical pMBRT treatments. The method established in this study will enable epidemiological studies of the long-term effects of intracranial treatments at ICPO, notably radiation-induced second malignancies.
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Affiliation(s)
- A M M Leite
- Institut Curie, PSL Research University, Radiation Oncology Department, Proton Therapy Centre, Centre Universitaire, F-91898 Orsay, France.,Institut Curie, PSL Research University, University Paris Saclay, Inserm U 1021- CNRS UMR 3347, F-91898 Orsay, France
| | - M G Ronga
- Institut Curie, PSL Research University, Radiation Oncology Department, Proton Therapy Centre, Centre Universitaire, F-91898 Orsay, France
| | - M Giorgi
- Institut Curie, PSL Research University, Radiation Oncology Department, Proton Therapy Centre, Centre Universitaire, F-91898 Orsay, France
| | - Y Ristic
- Institut de Radioprotection et de Sûreté Nucléaire, Service de Dosimétrie, Laboratoire de Dosimétrie des Rayonnements Ionisants, F-92262 Fontenay-aux-Roses Cedex, France
| | - Y Perrot
- Institut de Radioprotection et de Sûreté Nucléaire, Service de Dosimétrie, Laboratoire de Dosimétrie des Rayonnements Ionisants, F-92262 Fontenay-aux-Roses Cedex, France
| | - F Trompier
- Institut de Radioprotection et de Sûreté Nucléaire, Service de Dosimétrie, Laboratoire de Dosimétrie des Rayonnements Ionisants, F-92262 Fontenay-aux-Roses Cedex, France
| | - Y Prezado
- Institut Curie, PSL Research University, University Paris Saclay, Inserm U 1021- CNRS UMR 3347, F-91898 Orsay, France
| | - G Créhange
- Institut Curie, PSL Research University, Radiation Oncology Department, Proton Therapy Centre, Centre Universitaire, F-91898 Orsay, France
| | - L De Marzi
- Institut Curie, PSL Research University, Radiation Oncology Department, Proton Therapy Centre, Centre Universitaire, F-91898 Orsay, France.,Institut Curie, PSL Research University, University Paris Saclay, Inserm LITO, F-91898 Orsay, France
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Masilela TAM, Delorme R, Prezado Y. Dosimetry and radioprotection evaluations of very high energy electron beams. Sci Rep 2021; 11:20184. [PMID: 34642417 PMCID: PMC8511248 DOI: 10.1038/s41598-021-99645-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 09/30/2021] [Indexed: 11/16/2022] Open
Abstract
Very high energy electrons (VHEEs) represent a promising alternative for the treatment of deep-seated tumors over conventional radiotherapy (RT), owing to their favourable dosimetric characteristics. Given the high energy of the electrons, one of the concerns has been the production of photoneutrons. In this article we explore the consequence, in terms of neutron yield in a water phantom, of using a typical electron applicator in conjunction with a 2 GeV and 200 MeV VHEE beam. Additionally, we evaluate the resulting ambient neutron dose equivalent at various locations between the phantom and a concrete wall. Through Monte Carlo (MC) simulations it was found that an applicator acts to reduce the depth of the dose build-up region, giving rise to lower exit doses but higher entrance doses. Furthermore, neutrons are injected into the entrance region of the phantom. The highest dose equivalent found was approximately 1.7 mSv/Gy in the vicinity of the concrete wall. Nevertheless, we concluded that configurations of VHEEs studied in this article are similar to conventional proton therapy treatments in terms of their neutron yield and ambient dose equivalent. Therefore, a clinical implementation of VHEEs would likely not warrant additional radioprotection safeguards compared to conventional RT treatments.
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Affiliation(s)
- Thongchai A M Masilela
- Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation radiobiologie et cancer, 91400, Orsay, France
- Université Paris-Saclay, CNRS UMR3347, Inserm U1021, Signalisation radiobiologie et cancer, 91400, Orsay, France
| | - Rachel Delorme
- Univ. Grenoble Alpes, CNRS, Grenoble INP, LPSC-IN2P3, 38000, Grenoble, France
| | - Yolanda Prezado
- Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation radiobiologie et cancer, 91400, Orsay, France.
- Université Paris-Saclay, CNRS UMR3347, Inserm U1021, Signalisation radiobiologie et cancer, 91400, Orsay, France.
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Sotiropoulos M, Prezado Y. A scanning dynamic collimator for spot-scanning proton minibeam production. Sci Rep 2021; 11:18321. [PMID: 34526628 PMCID: PMC8443660 DOI: 10.1038/s41598-021-97941-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 09/01/2021] [Indexed: 11/23/2022] Open
Abstract
In proton minibeam radiation therapy, proton minibeams are typically produced by modulating a uniform field using a multislit collimator. Multislit collimators produce minibeams of fixed length and width, and a new collimator has to be manufactured each time a new minibeam array is required, limiting its flexibility. In this work, we propose a scanning dynamic collimator for the generation of proton minibeams arrays. The new collimator system proposed is able to produce any minibeam required on an on-line basis by modulating the pencil beam spots of modern proton therapy machines, rather than a uniform field. The new collimator is evaluated through Monte Carlo simulations and the produced proton minibeams are compared with that of a multislit collimator. Furthermore, a proof of concept experiment is conducted to demonstrate the feasibility of producing a minibeam array by repositioning (i.e. scanning) a collimator. It is concluded that besides the technical challenges, the new collimator design is producing equivalent minibeam arrays to the multislit collimator, whilst is flexible to produce any minibeam array desired.
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Affiliation(s)
- Marios Sotiropoulos
- Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400, Orsay, France.
| | - Yolanda Prezado
- Institut Curie, Université PSL, CNRS UMR3347, Inserm U1021, Signalisation Radiobiologie et Cancer, 91400, Orsay, France
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Charyyev S, Artz M, Szalkowski G, Chang C, Stanforth A, Lin L, Zhang R, Wang CC. Optimization of hexagonal‐pattern minibeams for spatially fractionated radiotherapy using proton beam scanning. Med Phys 2020; 47:3485-3495. [DOI: 10.1002/mp.14192] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 04/03/2020] [Accepted: 04/05/2020] [Indexed: 12/17/2022] Open
Affiliation(s)
- Serdar Charyyev
- Medical Physics Program Georgia Institute of Technology Atlanta GA 30332 USA
- Department of Radiation Oncology Emory University Atlanta GA 30322 USA
| | - Mark Artz
- UF Health Proton Therapy Institute Jacksonville FL 32206 USA
| | - Gregory Szalkowski
- Medical Physics Program Georgia Institute of Technology Atlanta GA 30332 USA
- Department of Radiation Oncology University of North Carolina Chapel Hill NC 27514 USA
| | - Chih‐Wei Chang
- Department of Radiation Oncology Emory University Atlanta GA 30322 USA
| | | | - Liyong Lin
- Department of Radiation Oncology Emory University Atlanta GA 30322 USA
| | - Rongxiao Zhang
- Department of Radiation Oncology Dartmouth College Hanover NH 03755 USA
| | - C.‐K. Chris Wang
- Medical Physics Program Georgia Institute of Technology Atlanta GA 30332 USA
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